数据驱动魔法师 何时迎来翻身日？

// before
TextView textView = findViewById(R.id.sample_text);
textView.setText(viewModel.getUserName());

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    // before
    // setContentView(R.layout.activity_main)
    
    // after
    val binding : ActivityMainBinding =
    DataBindingUtil.setContentView(this, R.layout.activity_main)
}

// DataBindingOptions.java
@Override
public boolean isEnabled() {
    // DataBinding 是否开启，对应上面在 build.gradle 中的配置
    return enabled;
}

// TaskManager 
protected void createDataBindingTasksIfNecessary(@NonNull VariantScope scope) {
    // 是否开启 DataBinding
    boolean dataBindingEnabled = extension.getDataBinding().isEnabled();
    boolean viewBindingEnabled = extension.getViewBinding().isEnabled();
    if (!dataBindingEnabled && !viewBindingEnabled) {
        // DataBinding 和 ViewBinding 均未开启则直接 return
        return;
    }
    createDataBindingMergeBaseClassesTask(scope);
    createDataBindingMergeArtifactsTask(scope);
    //...
    // 构建 DataBinding 相应绑定类
    taskFactory.register(new DataBindingGenBaseClassesTask.CreationAction(scope));
}
// CreationAction
override fun handleProvider(taskProvider: TaskProvider<out DataBindingGenBaseClassesTask>) {
    variantScope.artifacts.producesDir(
        // DATA_BINDING_BASE_CLASS_SOURCE_OUT
        InternalArtifactType.DATA_BINDING_BASE_CLASS_SOURCE_OUT,
        BuildArtifactsHolder.OperationType.INITIAL,
        taskProvider,
        DataBindingGenBaseClassesTask::sourceOutFolder
	)
}

public final class FragmentSingleChildBinding implements ViewBinding {
  // NonNull 注解标记
  // 如果存在不同配置的不同布局文件（如横竖屏）且该控件不是存在于所有布局，该处使用 Nullable注解标记
  @NonNull
  public final MaterialButton button;
    
  // 省略...
    
  @NonNull
  public static FragmentSingleChildBinding bind(@NonNull View rootView) {
    String missingId;
    missingId: {
      //其内部也是使用 findViewById
      MaterialButton button = rootView.findViewById(R.id.button);
      if (button == null) {
        missingId = "button";
        break missingId;
      }
      return new FragmentSingleChildBinding((MaterialButton) rootView, button);
    }
    throw new NullPointerException("Missing required view with ID: ".concat(missingId));
  }
}

public class MainActivity extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

		// Before Data Binding
		//setContentView(R.layout.activity_main);
        
		//TextView firstName = (TextView) findViewById(R.id.firstName);
		//TextView lastName = (TextView) findViewById(R.id.lastName);

		//firstName.setText("xxx");
		//lastName.setText("xxx");


		// After Data Binding
        ActivityMainBinding binding = DataBindingUtil.setContentView(this, R.layout.activity_main);

        binding.firstName.setText("xxx");
        binding.lastName.setText("xxx");
    }
}

public class MainActivity extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        ActivityMainBinding binding = DataBindingUtil.setContentView(this, R.layout.activity_main);
		binding.user = new User("xxx","xxx");
    }
}

@BindingAdapter({"imageUrl", "error"})
public static void loadImage(ImageView view, String url, Drawable error) {
  Glide.with(view).load(url).error(error).into(view);
}

class ViewModelActivity extends AppCompatActivity {
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        UserBinding binding = DataBindingUtil.setContentView(this, R.layout.user);

        binding.setLifecycleOwner(this);
    }
}

// TextViewBindingAdapter.java
@BindingAdapter(value = {"android:beforeTextChanged", "android:onTextChanged",
        "android:afterTextChanged", "android:textAttrChanged"}, requireAll = false)
public static void setTextWatcher(TextView view, final BeforeTextChanged before,
        final OnTextChanged on, final AfterTextChanged after,
        final InverseBindingListener textAttrChanged) {
    final TextWatcher newValue;
    if (before == null && after == null && on == null && textAttrChanged == null) {
        newValue = null;
    } else {
        newValue = new TextWatcher() {
            @Override
            public void beforeTextChanged(CharSequence s, int start, int count, int after) {
                if (before != null) {
                    before.beforeTextChanged(s, start, count, after);
                }
            }
            @Override
            public void onTextChanged(CharSequence s, int start, int before, int count) {
                if (on != null) {
                    on.onTextChanged(s, start, before, count);
                }
                if (textAttrChanged != null) {
                    //通知发生变化
                    textAttrChanged.onChange();
                }
            }
            @Override
            public void afterTextChanged(Editable s) {
                if (after != null) {
                    after.afterTextChanged(s);
                }
            }
        };
    }
    final TextWatcher oldValue = ListenerUtil.trackListener(view, newValue, R.id.textWatcher);
    if (oldValue != null) {
        view.removeTextChangedListener(oldValue);
    }
    if (newValue != null) {
        view.addTextChangedListener(newValue);
    }
}

// TextViewBindingAdapter.java
@InverseBindingAdapter(attribute = "android:text", event = "android:textAttrChanged")
public static String getTextString(TextView view) {
    return view.getText().toString();
}